Counterbalanced crane



N April 29, 1930. H. E. SWENSON COUNTERBALANCED CRANE Filed May 16, 1928 .llllllI'I INVENTOE.

. E. SWENSON.

' Patented Apr. 29, was

PATENT crates A HAROLD E. SWENSON, OF VALLEJO, CALIFORNIA GOUNTERBALANCED CRANE Application filed May 16,

Myinvention relates to improvements in cranes and particularly in cranes of the revolving deck type wherein a counterweight is slidably mounted in connection with the deck 5 and arranged to be moved by the boom actuating mechanism of the crane for shifting the cenger of gravity of the crane relatively to a loa The primary object of my invention is to provide an improved counter-balanced crane. Another object is to provide an improved crane wherein counter-weights may be moved "to shift the center of gravity of the crane to congorm to the weight and position of the loa Another object is to provide an improved counter-weight and shifting means which will operate simultaneously with the shifting of the boom to move the weights and thereby shift the center of gravity of the crane proportionally to the shifting of the load. V A further object is to provide an improved device of the character described wherein a counter-weight is normally carried in a posi- 7 tion embracedwithin the normal dimensions of the crane and is arranged to be extended to outwardly extending counter-balancing position whereby the lifting capacity of a crane of stated size and capacity may be increased to care for a substantial overload by keepingthe center of gravity within the base support of the crane when subjected to such overload.

Another object is to provide an improved mechanism whereby the counter-balance may be shifted by the boom actuating mechanism either independently, or simultaneously andautomatically with the boom. 7

A further object is to provide an improved device which may be installed upon cranes of standard construction without altering or interferingwith the normal operation of such cranes and which will materially increase the eflicieney of the crane.

A still further object is to provide an improved device of the character described which is simple in construction and positive "andetficient in its operation.

I accomplish these and other objects by 1928. Serial No. 278,293.

means of the improved device disclosed in the drawings forming a part of the present application wherein like characters of reference are used to designate similar parts throughout the specification and drawings and in which Fig. 1 is a side elevation of my improved counter-balanced crane.

I Fig. 2 is a rear elevation of the counterbalance mechanism as applied upon the deck 6 of a revolving deck crane in connection with the actuating mechanism of the crane, the engine and hoisting mechanism, other than the boom actuating drum, being omitted; and

Fig. 3 is a broken side elevation of the counter-weight actuating gearing.

Referring to the drawings, the numeral 1 is used to designate in general a crane of the portable revolving deck type provided with the usual mast 2, boom 3, and power mechanism 4 mounted upon a deck 6 revolvably mounted upon a truck body 7. The deck 6 is arranged to be rotated relative to the supporting truck body 7 by means of a gear 8 in the ordinary manner. The power 7 mechanism, designated in general by the numeral 4: includes the usual boom controlling drum 9 arranged to take in or pay out a cable 11 for raising and lowering the boom 3 which is pivotally mounted upon one end of the deck :3 6 in the well known manner. The boom 3 is also provided with the usual hoisting means including a hoisting drum 12 and cable 13 operating over the usual pulley blocks 14 and 16 for hoisting loads relative to the end of the boom in the usual manner.

In a crane of the, type illustrated, the supporting base is necessarily limited, and when the boom is extended to its extreme reach '90 and subjected to a heavy load the center of gravity of the load crane is shifted toward the side or end of the base from which the boom extends. The load which may be lifted by the boom must be limited to prevent the center of gravity from being shifted outside the base of the crane and the crane tipped over. This is particularly true when the boom is swung outwardly toward one side of the base, and as such cranes are commonly shifted from V .ly faced flanges'of the channel bers 17. A plurality-of the Height 7 members 17v and varied to suit a Weight consists of a pair of frame ineinb criving gears installed without altering place to place when in service, it is inconvenient to anchor the crane.

In my present invention 1 provide a counter-weight arranged to be moved to counter-balance the weight of the load and to shift the center of gravity of the crane proportionally to the shifting of a load, thereby keeping the center of'gravity nearthe center of the crane base at all times. The con A 2-1 are provided to provide a desired 7 which may be ad usted relatively to the i f 211v) 1 space between thel'fra'me' .members 1 join theiends'of said members to forms y, shaped counter-weight; 7 The members arranged to extend between the membe immediately-below the decks and a e arranged to be received within the space tween said deck and the top of the supporting "truck body 7; V

The counter-weight is arranged to be fmo'ved by power from the boom controlling drum 9 and its actuating means preferably by means of racks 23 secured upon theframe members 17 and engaged'by pinions driven by gears 26 which in turn are driven by pinions 27 meshing with gears 28 and 29 mount- ,ted upon the driven and the driving portions respectively of thedrum 9.. The pi ions 27 are rotatably mounted upon ash aft 31 en en'd ing transversely across the deckfi and vided'with suitable'clutches 32 and 33 arranged to secure the adjacent pinion to l n3 shaft whereby theshaft- 31 and the gears and pinions 24: and 26 may-be driven by either thefldriven or driving portions of the drum 9. p The gears 26: and pinions 2d are arranged to provide asnitable speed reduction between .the drum 9 and the racks 23f In operation, the framemembers 17 ar mounted upon thesides of t i the ordinary construction and operation of the. crane. The weight members 21 are mounted upon the ends of the frame members so as to be positioned normally between the under side of'the deck 6 the top of the truck body the deck and 7so that the length of the crane not be increased and the deck maybe rotated in the 'ing shalt.

1 claim as new and desire to secure by Letters ordinary manner Without interference by the weights.

When the boom is extended to lift a load the counter-weight is moved by the actuating gear connections to extend the frame members 17 and the weight-s2lcarried thereby longitudinally outward from theend of the deck 5 opposite the boom 3. This is accomplished by moving one of the clutches 32 or a 33 to lock the ad1acentpinion 27 to the dr1vc When theclutch 32 is moved to lock the pinion 2'? driven by the driven portion of the drum 9, the rotation of said drum in paying out the cable 11 to lower the boom 3 will cause the counter weight frame to be moved outwardly to the p osition shown in full lines in'Fig. l ef the drawings, ,thereoy counter-balancing the boom and shifting the center of gravity of thecrane rearwardly to balance the weight of therboomand a load lifted tiereby As the boomis raised,-the. counter-weight will be moved inwardly proportionally to the inward movement of the boom indicated in detted'lines and its load so that the center-of gravity will be maintained at the approximate center of the crane as the boom is shifted, the counterweight being moved outwardly and inwardly simultaneously with tlrelowering and raising of t is boom to automatically compensate for. the shifting ofthe load.

If it is desired to move the counter-weight to extended :position'and to maintain it in such extended position, the clutch 33 may be moved to connect the-pinion 27dr1ven by the driving memberi29 of the drum;9, thereby moving the counter-weight independently of the movement or the' drum, or the counterweight may bemoved outwardly; as the boom is lowered and the clutch 32 disengaged so as to leave the counter weight so extended.

Whenthe counter-weight is in extended p'osition, the center of gravity of the'crane is so shifted thata much greater load can be lifted by the boom without over balancing the crane,

thus materially increasing the lifting capacity of the crane without altering the design thereof. When in normal position, the counter-weight is embraced within the 11atu ral area of the crane, thus permitting the crane to be transported with the usualfacility.'

Vhilel have illustrated and described only the preferred form-and construction of the device, the several elements are subject to modification in numerous ways without de parting from the spirit of my invention. I therefore do not wish to restrict myself to the specific details and mode of operation illustrated and described, but desire to avail self of all modifications which may fall within the scope of the appended claims.

1 Having thus described my invention what Patent is a e 1. In a crane, the combination With a deck, a movable boom mounted upon one end of the deck, and boom actuating mechanism mounted upon the deck, of a counter-Weight mounted upon the opposite end of the deck, said counter-Weight comprising a pair of frames members slidably mounted along the sides of the deck and a counter-Weight body mounted upon the outer ends of the frame members and connecting the same; means for moving the counter-Weight to shift the center of gravity of the crane relative to a load; and anti-friction rollers mounted upon the frame members and engaging the sides .of the deck to facilitate movement of the counter-Weight.

2. In a crane, the combination With a deck,

a movable boom mounted upon one end of the deck, and boom actuating mechanism mounted upon the deck, of a counter-Weight mounted upon the opposite end of the deck, said counter-Weight comprising a pair-of frame members slidably mounted upon the sides of the deck and a counter-Weight body connected between the ends of the frame members and joining the same in the form of a yoke, said counter-Weight body being movable from a normal position extending under the deck to an extended position extending outwardly from the end of said deck; and means for moving the counter-Weight to shift the center of gravity of the crane relatively to a load.

In Witness whereof, I hereunto set my signature.

HAROLD E. SWENSON. 

